This invention relates to lifting magnets and, more particularly, to an improved means for protecting component parts of a lifting magnet from cracking, buckling, or otherwise being damaged due to internal stress resulting from thermal expansion of the lifting magnet and its encapsulating material.
One solution for solving the thermal expansion problem is shown in U.S. Pat. No. 3,763,453 which issued on Oct. 2, 1973. In this patent, a hermetically sealed tubing is wound around the magnet coil and secured in place by taping it to the coil before the coil is encapsulated in the encapsulating material or potting compound in a manner known in the art. This tubing is flexible and compressible and absorbs the thermal expansion of the coil and its encapsulating material during the operation of the lifting magnet to prevent cracking of the magnet case. However, the use of a single sealed tubing has several problems and one of these problems is that if any portion of the tubing is perforated in the course of fabrication or assembly of the coil and magnet, or during encapsulation, the entire tubing becomes inoperative.